>>> [!note] Migrated issue <!-- Drupal.org comment --> <!-- Migrated from issue #3631203. --> Reported by: [marcofernandes](https://www.drupal.org/user/2127558) Related to !302 !301 >>> <h3 id="summary-problem-motivation">Problem/Motivation</h3> <p>Previewing a pattern that contains a content block creates a copy of that content block.</p> <p>The <code>drupalgutenberg/duplicate-content-block-ids</code> filter (<code>editor.BlockEdit</code>, <code>js/filters/content-blocks.jsx</code>) runs for every content block that is rendered, including the blocks of the previews of the inserter's Patterns tab. A preview's content block has a new client ID, so the filter calls <code>/editor/content_block/clone_if_used</code>, and <code>GutenbergContentBlocksManager::cloneBlock()</code> saves a copy of the block when it is already used: by another node, or by the edited one when the same block is already in the content (<code>isDuplicate</code>). The copy is never used, as the preview is discarded.</p> <p>On a test site with 20 non-reusable content blocks and 40 patterns (2 content blocks each, in 4 categories), browsing the 4 categories once created 60 content blocks, and every visit creates more. Each one also costs a request, on top of the render requests of the preview.</p> <p>The copies have an inactive usage record, so <code>gutenberg_cron()</code> deletes them, but only after 24 hours and 20 per run, so they pile up faster than cron removes them on sites where editors browse patterns.</p> <p>Only non-reusable content blocks are copied (<code>canBeCloned()</code>), which are the ones the editor creates. For reusable ones, the request still runs and the preview clears the block's ID.</p> <p>4.0.x has the same filter (<code>packages/filters/src/content-blocks.jsx</code>).</p> <h3 id="summary-steps-reproduce">Steps to reproduce</h3> <ol> <li>Allow the Basic content block type for Basic page.</li> <li>Create a Basic page, add a Basic content block, fill in its form in the sidebar, and save the page.</li> <li>Edit the page again, select the content block, and create a pattern from it (Options &rarr; Create pattern).</li> <li>Count the content blocks: <code>drush sqlq "SELECT COUNT(*) FROM block_content"</code></li> <li>Open the block inserter, Patterns tab, and select the pattern's category.</li> <li>Count the content blocks again: there is one more. Selecting the category again adds another.</li> </ol> <h3 id="summary-proposed-resolution">Proposed resolution</h3> <p>Skip the duplicate check in previews. A preview has its own block editor settings with the preview mode on, so the filter can read it from the block editor store, under both names the setting has had: <code>__unstableIsPreviewMode</code> (the WordPress 6.4 packages of 3.0.x) and <code>isPreviewMode</code> (since WordPress 6.8, used by 4.0.x).</p> <p>The check still runs when a pattern is inserted, as its blocks are then created in the content.</p> <p>Also remove the filter's <code>console.log()</code> calls.</p> <h3 id="summary-remaining-tasks">Remaining tasks</h3> <ul> <li>Fix the filter on 3.0.x and 4.0.x.</li> <li>Add a test: preview a pattern with a used content block and check that no content block is created.</li> <li>Follow-ups for the request load of the editor (to be opened): <ul> <li>Since 3.0.7, the hydration code in <code>gutenberg.js</code> calls <code>resetBlocks()</code> on every editor load, so every Drupal block and content block is fetched twice.</li> <li>Rendered Drupal blocks, rendered content blocks and the view mode lists aren't cached, on the client or the server, so each preview and each block fetches them again.</li> </ul> </li> </ul> <h3 id="summary-ui-changes">User interface changes</h3> <p>None.</p> <h3 id="summary-api-changes">API changes</h3> <p>None.</p> <h3 id="summary-data-model-changes">Data model changes</h3> <p>None. Copies created so far are deleted by cron.</p>